Various compounds have been used in the past as primers or coupling agents for adhering all types of polymers to glass. One such compound is N-[beta-(N'-paravinylbenzyl)-aminoethyl]-gamma-aminopropyltrimethoxysilane hydrochloride claimed in U.S. Pat. No. 3,734,763 and described in Applied Polymer Symposium, 19, 75 (1972) as a virtually universal coupling agent and adhesion promoter for almost all plastics to almost all rigid surfaces. However, such a coupling agent when used alone especially to adhere vinyl polymers to glass does not provide a bond which will resist alkali satisfactorily.
In U.S. Pat. No. 3,674,542, glass fibers are coated with a liquid composition consisting of 1 to 10 weight percent of a vinylic aromatic and a diolefin (such as styrene-butadiene copolymer) and 0.2 to 2 weight percent of a hydrolyzable silane such as gamma-aminopropyltriethoxysilane. The adhesion obtained before alkali immersion of the coating is reported to be excellent and the patentees state that the silane is essential to get adhesion.
More recently, mixtures of resins and silanes have been marketed commercially as coupling agents for various polymers and glass. Typical of such mixtures are XZ8-5066 available from Dow-Corning Corporation, Midland, Michigan which contains 8.4 parts by weight of an epichlorohydrin-bisphenol A resin having an epoxide equivalent of 182 to 189 and 1.6 parts by weight of N-aminoethylgamma-aminopropyltrimethoxysilane (Z-6020) in 45 parts by weight each of ethyleneglycolmonomethylether and ethyleneglycolmonoethylether acetate which is said by the makers to be useful for coupling polyurethanes and other thermosetting resins to glass.
Another mixture available from Dow-Corning is XZ8-5080 which is a 50% by weight latex of 55 mol percent styrene and 45 mol percent butadiene containing 2 percent by weight of Z-6020 which is useful for coupling styrene-butadiene copolymers and other thermoplastic resins such as polyolefins to glass.
Despite the virtues of the coupling agents hereinbefore described, the adhesion obtained between the polymer and glass is not always acceptable when the coated glass is washed in dilute alkali. In other words, adhesion of a particular polymer to glass is still an individual problem since no single coupling agent is satisfactory in all cases. It is therefore the object of this invention to develop a stronger bond between rubbery copolymers and glass which will resist alkali and render a glass container so coated virtually shatterproof if accidentally dropped.